screens tubes

A cathode ray tube is a device that uses a beam of electrons in order to produce an image on a screen. Cathode ray tubes are also known commonly as CRTs. Cathode ray tubes are widely used in a number of electrical devices, such as computer screens, television sets, radar screens, and oscilloscopes used for scientific and medical purposes. A cathode ray tube consists of five major parts: an envelope or container, an electron gun, a focusing system, a deflection system, and a display screen.

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Most people have seen a cathode ray tube or pictures of one. The "picture tube" in a television set is perhaps the most familiar form of a cathode ray tube. The outer shell that gives a picture tube its characteristic shape is called the envelope of a cathode ray tube. The envelope is most commonly made of glass, although tubes of metal and ceramic can also be used for special purpos…

Under normal circumstances, an electron beam produced by the electron gun described above would have a tendency to spread out to form a cone-shaped beam. However, the beam that strikes the display screen must be pencil-thin and clearly defined. In order to form the electron beam into the correct shape, an electrical or magnetic lens, similar to an optical lens, can be created adjacent to the accel…

The actual conversion of electrical to light energy takes place on the display screen when electrons strike a material known as a phosphor. A phosphor is a chemical that glows when exposed to electrical energy. A commonly used phosphor is the compound zinc sulfide. When pure zinc sulfide is struck by an electron beam, it gives off a greenish glow. The exact color given off by a phosphor also depen…

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